It has been reported by the American Heart Association (1995 Statistical Supplement), that there are about 60 million adults in the United States that have cardiovascular disease, including 11 million adults who have coronary heart disease. Cardiovascular diseases are responsible for almost a million deaths annually in the United States, representing over 40% of all deaths. In 1995, 1.5 million adults in the United States will carry the diagnosis of angina pectoris, experiencing transient periods of myocardial ischemia resulting in chest pain. About 350,000 new cases of angina occur each year in the United States.
Myocardial ischemia occurs when the heart muscle does not receive an adequate blood supply and is thus deprived of necessary levels of oxygen and nutrients. The most common cause of myocardial ischemia is atherosclerosis, which causes blockages in the blood vessels (coronary arteries) that provide blood flow to the heart muscle. Present treatments include pharmacological therapies, coronary artery bypass surgery and percutaneous revascularization using techniques such as balloon angioplasty. Standard pharmacological therapy is predicated on strategies that involve either increasing blood supply to the heart muscle or decreasing the demand of the heart muscle for oxygen and nutrients. Increased blood supply to the myocardium is achieved by agents such as calcium channel blockers or nitroglycerin. These agents are thought to increase the diameter of diseased arteries by causing relaxation of the smooth muscle in the arterial walls. Decreased demand of the heart muscle for oxygen and nutrients is accomplished either by agents that decrease the hemodynamic load on the heart, such as arterial vasodilators, or those that decrease the contractile response of the heart to a given hemodynamic load, such as beta-adrenergic receptor antagonists. Surgical treatment of ischemic heart disease is based on the bypass of diseased arterial segments with strategically placed bypass grafts (usually saphenous vein or internal mammary artery grafts). Percutaneous revascularization is based on the use of catheters to reduce the narrowing in diseased coronary arteries. All of these strategies are used to decrease the number of, or to eradicate, ischemic episodes, but all have various limitations.
Preliminary reports describe new vessel development in the heart through the direct injection of angiogenic proteins or peptides to treat myocardial ischemia. The several members of the fibroblast growth factor (FGF) family (namely acidic fibroblast growth factor, aFGF; basic fibroblast growth factor, bFGF; fibroblast growth factor-5, FGF-5 and others) have been implicated in the regulation of angiogenesis during growth and development. The role of aFGF protein in promoting angiogenesis in adult animals, for example, was the subject of a recent report. It states that aFGF protein, within a collagen-coated matrix, placed in the peritoneal cavity of adult rats, resulted in a well vascularized and normally perfused structure (Thompson, et al., PNAS, 86:7928-7932, 1989). Injection of bFGF protein into adult canine coronary arteries during coronary occlusion reportedly led to decreased myocardial dysfunction, smaller myocardial infarctions, and increased vascularity in the bed at risk (Yanagisawa-Miwa, et al., Science, 257:1401-1403, 1992). Similar results have been reported in animal models of myocardial ischemia using bFGF protein (Harada, et al., J. Clin. Invest., 94:623-630, 1994, Unger, et al., Am. J. Physiol., 266:H1588-H1595, 1994).
A prerequisite for achieving an angiogenic effect with these proteins however, has been the need for repeated or long term delivery of the protein, which limits the utility of using these proteins to stimulate angiogenesis in clinical settings. In other words, successful therapy in humans would require sustained and long-term infusion of one or more of these angiogenic peptides or proteins, which are themselves prohibitively expensive and which would need to be delivered by catheters placed in the coronary arteries, further increasing the expense and difficulty of treatment.
Recently, various publications have postulated on the uses of gene transfer for the treatment or prevention of disease, including heart disease. See, for example, Mazur, et al., "Coronary Restenosis and Gene Therapy", Molecular and Cellular Pharmacology, 21:104-111, 1994; French, "Gene Transfer and Cardiovascular Disorders", Herz, 18:222-229, 1993; Williams, "Prospects for Gene Therapy of Ischemic Heart Disease", American Journal of Medical Sciences, 306:129-136, 1993; Schneider and French, "The Advent of Adenovirus: Gene Therapy for Cardiovascular Disease", Circulation, 88:1937-1942, 1993. Another publication, Leiden, et al., International Patent Application Number PCT/US93/11133, entitled "Adenovirus-Mediated Gene Transfer to Cardiac and Vascular Smooth Muscle," reports on the use of adenovirus-mediated gene transfer for the purpose of regulating function in cardiac vascular smooth muscle cells. Leiden, et al. states that a recombinant adenovirus comprising a DNA sequence that encodes a gene product can be delivered to a cardiac or vascular smooth muscle cell and the cell maintained until that gene product is expressed. According to Leiden, et al., muscle cell function is regulated by altering the transcription of genes and changes in the production of a gene transcription product, such as a polynucleotide or polypeptide. That polynucleotide or polypeptide, report Leiden, et al., interacts with the cardiac or smooth muscle cell to regulate function of that cell. Leiden, et al. states that this regulation can be accomplished whether the cell is situated in vitro, in situ, or in vivo. Leiden, et al. describes a gene transfer method comprising obtaining an adenoviral construct containing a gene product by co-transfecting a gene product-inserted replication deficient adenovirus type 5 (with the CMV promoter) into 293 cells together with a plasmid carrying a complete adenovirus genome such as plasmid JM17; propagating the resulting adenoviral construct in 293 cells; and delivering the adenoviral construct to cardiac muscle or vascular smooth muscle cells by directly injecting the vector into the cells.
There are impediments to successful gene transfer to the heart using adenovirus vectors. For example, the insertion of a transgene into a rapidly dividing cell population will result in substantially reduced duration of transgene expression. Examples of such cells include endothelial cells, which make up the inner layer of all blood vessels, and fibroblasts which are dispersed throughout the heart. Targeting the transgene so that only the desired cells will receive and express the transgene, and the transgene will not be systemically distributed, are also critically important considerations. If this is not accomplished, systemic expression of the transgene and problems attendant thereto will result. For example, inflammatory infiltrates have been documented after adenovirus-mediated gene transfer in liver (Yang, et al., Proc. Natl. Acad. Sci. (U.S.A.), 91:4407, 1994). Finally, with regard to adenovirus-mediated gene transfer of FGF-5 for the in vivo stimulation of angiogenesis, we have discovered that the injected viral material can induce serious, often life-threatening cardiac arrhythmias.
The invention described and claimed herein addresses and overcomes these and other problems associated with the prior art.